IgA has been known as a molecule present in saliva, intestine, trachea and the like, which has an important role in enhancing barrier functions of mucosa such as blocking microorganisms and allergen which penetrate through mucosa such as intraoral or intestinal mucosa or the like. Additionally IgA protect an immunologically immature infantile body and it has been well known that IgA from mother's milk is used for immunological compensation as passive immunity.
On the other hand, regarding immunomodulatory functions of lactic acid bacteria, there have recently been several reports and information about mechanisms, and differences among species or strains have been increasingly elicited (Tetsuji Hirota: New Food Industry, Vol. 32, No 10, p 9 (1990)). However, in these reports, not all the immunomodulatory functions were covered and not all species of lactic acid bacteria have been discussed. Thus only insufficient information has been obtained without comprehension of the overview. Lactic acid bacteria which promote secretion of IgA have been partially discussed and particularly bacteria of genus Bifidobacterium is considered to have some role in infants, since the abundance ratio thereof in infantile feces is high. There is an attempt of co-culturing Bifidobacterium bacteria with Peyer's patch cells to select bacteria with high activity to induce IgA production. Specifically, presence of strains of Bifidobacterium longum and Bifidobacterium breve having strong promoting activity on IgA secretion were reported (JP 02-280059). However, Bifidobacterium bacteria have been known to be present scarcely in human adult intestine, and therefore it is expected that normally they hardly contact Peyer's patch cells. Indeed, such species or strains individually selected have not been confirmed about whether they sufficiently function in human intestine.
Having reviewed lactic acid bacteria in general, there are no reports suggesting relationship between Lactobacillus bacteria and IgA production, specifically there are no reports about attempts to compare IgA production-promoting activities among Lactobacillus species or strains which are abundant in intestine where Peyer's patch having important role in gut immunity exits and which have high localization in order to find species or strains having high activity. Regarding the intestinal localization of Lactobacillus bacteria in human, Lactobacillus amylovorus (L. amylovorus) was reported to be a lactic acid bacteria belonging to genus Lactobacillus which is dominant in human flora as well as Lactobacillus paracasei, Lactobacillus gasseri and Lactobacillus johnsonii (Bioscience Microflora, 22 (3), 75-83, 2003).